Although applicable in principle to arbitrary contact-connections, the present invention and also the problem area on which it is based will be explained with regard to releasable contact-connections in test structures.
The integration density of semiconductor memory chips and of other semiconductor components is rising to an increasing extent. This leads to an increasing complexity of the methods for fabricating the memory elements, inter alia due to an increased number of individual processing steps, and also due to the reduction of the feature sizes. Test methods that can check whether a component has the desired functions as early on as possible in the fabrication method are of considerable interest for cost reasons. Before the individual components are sawn out from a wafer, their electrical properties and functions have already been completely defined. Therefore, this is an advantageous moment for contact-connecting the individual components and subjecting them to a test method corresponding to their function.
In order to test a component with regard to its functionality, it has to be connected to a suitable measuring apparatus. In a conventional method, for this purpose individual test tips are typically pressed onto electrical contacts of a component. For this purpose, the individual test tips have to be moved individually to the correct position with a high outlay.
A further test method provides for testing the individual components that have already been sawn but are still unpackaged. For this purpose, it is likewise necessary to provide suitable contact-connections which enable a simple yet nonetheless reliable contact-connection.
An expedient sensor that touches all the relevant contacts of a component and connects them to the measuring apparatus is pressed onto a component. Consequently, instead of a multiplicity of test tips, only one measuring sensor is moved over the wafer. Since the components on a wafer are typically all structurally identical, the one measuring sensor can be used for all the components. For this purpose, however, the measuring sensor must reliably connect each individual contact of an individual component to the measuring apparatus. Using elastic contacts on the part of the component and/or on the part of the measuring sensor ensures that all the connections are produced.
FIG. 5a shows a schematic illustration for elucidating the problem area of an elastic contact-connection such as is known inter alia from DE 100 16 132. This elastic contact-connection has an elastic elevation 3, on which a contact region 20 is applied to a roof area 6 that is planar to the greatest possible extent. The contact region is connected to structures 12 on the component via a conductor track 10. If a mating contact is pressed onto the contact region 20, the elastic elevation 3 yields. The elasticity of the elevation 3 ensures that the contact region 20 remains pressed against the mating contact. Unevennesses in a component are compensated for by the fact that the individual mechanical elevations 3 of different contact regions 20 are pressed together to different extents, so that all the individual contact regions 20 are connected to their corresponding mating contacts.
What is disadvantageous about this device is that the conductor track 10 is damaged with repeated compression of the elastic elevation 3. This is a consequence of compression of the conductor track 10. In this case, the conductor track 10 typically detaches from the elastic elevation 3, as illustrated in FIG. 5b. In this case, the conductor track 10 is locally compressed and/or buckled. Repeated compression of the conductor track 10 as a result of multiple contact-connection such as would occur in a test setup, for example, therefore leads to fatigue of a material of the conductor track 10 through to irreparable damage to the conductor track 10.
A further loading on the conductor track 10 is produced by that portion 40 of the elastic material which, on account of the pressed-together elevation, yields to the greatest possible extent uniformly on all sides, as indicated in FIG. 5b. The portions that bulge out beneath the conductor track 10 in this case lead to mechanical loading on the conductor track 10.